1. Field of the Invention
The present invention relates to controlling a print operation for an ink jet printer based on print head temperature. In particular, the invention pertains to controlling the print operation so as to cool an ink jet print head before capping.
2. Description of the Related Art
Conventional ink jet printers utilize a print head with a plurality of nozzles that are supplied with ink by internal ink supply tubes. The ink from the ink supply tubes forms a meniscus in each nozzle. A heating element is disposed behind each nozzle, and ink is ejected from a nozzle by firing the corresponding heating element. The firing of the heating element boils the ink, thereby forming a bubble of ink that is ejected from the nozzle, resulting in a dot, or pixel, on a recording medium. Thus, by controlling the firing of the heating elements, an image is formed on the recording medium.
Typically, at the conclusion of a print job or upon power-off, conventional ink jet printers move their print head (or heads) to a home position where it waits for the next print job and/or power-on. At the home position, the print head is cleaned and capped so as to protect the sensitive print head and to keep ink from drying on the outside of the print head. The capping mechanism also protects the print head from damage when servicing the printer. In addition, the capping mechanism typically includes a device for sucking ink from the print head to help keep the print head clean.
These conventional systems suffer from a problem in that the print head is often very hot when the print head is capped, resulting in hot ink being confined by the cap in the nozzles and in the ink supply tubes of the print head. In some instances, this hot ink dries out or does not form a proper meniscus in each of the nozzles of the print head due to a change in viscosity. As a result, the confined hot ink can form unwanted deposits in and on outer portions of the nozzles (i.e., beyond where the meniscus should form) and on the print head, and these ink deposits can then thicken or dry. The thickened or dried ink deposits can interfere with proper operation of the print head, resulting in poor print quality. Accordingly, it is desirable to cap the print head after the ink and the print head have cooled.